Yoshida K I, Oshima H, Troen P
J Clin Endocrinol Metab. 1980 May;50(5):895-9. doi: 10.1210/jcem-50-5-895.
A NADH-linked 17 alpha-hydroxylation of progesterone was examined using the washed microsome fraction prepared from human testes. The addition of NADP revealed no enhancement of 17 alpha-hydroxylation, indicating no transhydrogenation from NADH to NADP in the microsome fraction. The results further substantiate the presence of NADH-linked activity of 17 alpha-hydroxylation in addition to NADPH-linked activity. The Km of 17 alpha-hydroxylase for NADH was calculated as 4.3 x 10(-5) M at pH 7.4 and 37 C. The optimal pH of 17 alpha-hydroxylase was 7.7 in the presence of NADH and 7.9 in the presence of NADPH. An additive increase in the amount of product 17 alpha-hydroxyprogesterone was observed by adding NADH to the incubation medium containing an excess amount of NADPH. The data suggest that there are two distinct active sites for 17 alpha-hydroxylation. Furthermore, the inhibition of NADH-linked 17 alpha-hydroxylation by carbon monoxide indicates the involvement of cytochrome P450 in the electron transport system for the NADH-linked 17 alpha-hydroxylation.
利用从人睾丸制备的洗涤微粒体部分，研究了与NADH相关的孕酮17α-羟化作用。添加NADP后，17α-羟化作用并未增强，这表明微粒体部分中不存在从NADH到NADP的转氢作用。这些结果进一步证实，除了与NADPH相关的活性外，还存在与NADH相关的17α-羟化活性。在pH 7.4和37℃条件下，17α-羟化酶对NADH的Km值计算为4.3×10(-5)M。在存在NADH的情况下，17α-羟化酶的最适pH为7.7；在存在NADPH的情况下，最适pH为7.9。通过向含有过量NADPH的孵育培养基中添加NADH，观察到产物17α-羟孕酮的量呈累加增加。数据表明，存在两个不同的17α-羟化活性位点。此外，一氧化碳对与NADH相关的17α-羟化作用的抑制表明，细胞色素P450参与了与NADH相关的17α-羟化作用的电子传递系统。
